JP2008506036A - Copper-containing conductive material with Me-DLC hard material coating - Google Patents

Abstract

  The present invention relates to a conductive material comprising a copper-containing alloy for use as an inset or clamp connection having a cover layer comprising at least a support layer and an adhesive layer deposited on at least a part of a contact surface, In this case, the anti-friction layer has a carbon content of 40 atomic% or more and 70 atomic% or less.

Description

TECHNICAL FIELD The present invention relates to an electrically conductive material comprising a copper-containing alloy for use as a plug-in or clamp-type connection according to the superordinate concept of claim 1. Furthermore, the contact piece according to claim 18, and the semi-finished product or the strip or profile according to claim 20.

Prior art Copper-containing alloys are also known from the prior art, as is the good suitability of the copper material for the application of a plating layer for surface treatment. On the other hand, PVD-, CVD- or PVD / CVD films have not been used to date with relatively soft copper materials, as can occur, for example, in the case of plug-in or clamp-on connections. This is because, in the case of a sliding load with a very high load, the film is pushed or pierced into the base metal, and many film systems used for tool coating have too high a coefficient of friction (for example, carbide WC or Cr _x C _y has a coefficient of friction greater than about 0.5), because it exhibits too high roughness or poor conductivity, which makes the film system less suitable for such use.

  German Offenlegungsschrift 180 29 932 discloses a high-frequency plasma method for coating electrical contacts with a carbide anti-wear film. Similar is DE 3011694, in which the application of a plating adhesive layer (galvanischen Haftschit) to various metal materials, in particular hardened or tempered, is followed by radio frequency plasma. PVD coatings are described, in which a carbide hard material film, in particular, is deposited. This achieves good electrical conductivity as well as increased wear protection, but in that case a relatively high coefficient of friction results from the carbide coating.

  From German Offenlegungsschrift 442 211 144, a coated coating in which a hard material film made of metal carbide first and subsequently an anti-friction film containing free carbon is applied to the tungsten carbide base in order to extend the tool life. Tools are known.

DISCLOSURE OF THE INVENTION The object of the present invention is to contain copper which avoids the above-mentioned drawbacks of the prior art and achieves better electrical properties and better tool life- and sliding properties over conventional coated materials. It is to provide a conductive material.

This problem is solved by the features according to the invention in the characterizing part of claim 1.
A carbon-containing anti-friction or hard layer, modified in accordance with the present invention, having a carbon content of 40 atomic percent or more but 70 atomic percent or less, which is deposited on copper or copper alloys, is used. By doing so, it is possible to increase the hardness of the surface and thus the wear and friction resistance of the material without changing its superior electrical properties essentially. In this case, the content of carbon bound or free as carbide is taken as the carbon content, which is supplemented to 100% with the carbide-forming material and any further elements. In this case, for example, a hard film with limited anti-friction and electrical properties is deposited using the following more detailed method, and this hard film extends the tool life of the conductive material. This film is slightly harder than conventional hard carbide films, but is significantly harder than the carrier material and thereby protects it from wear. Surprisingly, this membrane protects the carrier material better than conventional hard membrane systems in the case of plug-in and clamp-in use, in which case it is additionally added for use with high pressure per unit area Another support layer may be provided. This is also considered to be due to the relatively low coefficient of friction in the case of the present hard film, this coefficient of friction preferably acting for example when used for plug-in connections, because at the same time the insertion force This is because the scratches on the relatives, which may be uncoated, may be prevented.

  Exactly these properties make such membranes suitable for use in vehicle- or aircraft assembly, i.e. any use where invariant loads due to vibration, vibration or the like sometimes occur with impact loads. . Surface fatigue at such joints that interferes with function or completely prevents function due to higher stability compared to conventional copper conductive materials, this surface fatigue is copper, that is, a pre-known coated copper Occurrences that can be caused by the relatively low strength of the material are avoided. Furthermore, the tribooxidation phenomenon that occurs at elevated operating temperatures and often causes such plug and clamp connection failures can also be effectively prevented.

  A significant improvement in load capacity has been observed with copper-containing alloys coated according to the present invention so far when used as plug and clamp connections: copper, bronze, brass or silver. However, similar improvements can be expected when using other base materials such as CuBe and other alloys or when used for other applications.

  Furthermore, it can be equally advantageous to use a conductive material pre-coated by plating. Examples thereof are Cr-, Ni- or CrNi films applied before the support layer.

  Due to the low deposition temperature, plasma CVD-, PVD- or PVD / CVD-hybrid processes are particularly suitable for the deposition of Me-DLC films, for example for coating of temperable copper material.

  However, of course, conventional membranes containing free carbon as described, for example, in German Offenlegungsschrift 442 211 144, or Me described in U.S. Pat. No. 4,992,153 or German Offenlegungsschrift 10018143. -DLC films (DLC means "diamond like carbon") cannot achieve sufficient conductivity, and also as in the case of known carbide films, for example Sufficient protection against being pushed into the base metal cannot be achieved. Surprisingly, a substantial improvement in conductivity could already be achieved simply by adjusting the carbon content to more than 40 atomic percent but not more than 70 atomic percent. Particularly good properties have been achieved with a carbon content above 50 atomic%, but below 60 atomic%.

Additions comprising elements of groups IV, V and VI of the periodic table (ie Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W) or at least one metal Me from aluminum or Si By applying a typical support layer, another indentation could be avoided even in the case of significantly higher loads. In doing so, it has proved to be particularly advantageous to have a support layer which, in addition to the metal phase, still contains nonmetals, for example C, N, B or O, and / or hard metal compounds of said metals with these nonmetals. is doing. Exclusively this case the support layer system TiN or Ti / TiN (i.e. metals titanium film and subsequent titanium nitride hard film) as an example, CrN or _Cr / CrN, Cr x _{C y} or Cr _/ Cr _x C y, Cr _x (CN) _y or Cr / Cr _x (CN) _y , TiAl or TiAlN and TiAl / TiAlN.

  Of course, however, care must be taken that the support layer has a minimum thickness depending on the use case. This depends inter alia on the pressure per unit area that arises depending on the use case. For example, when the pressure per unit area is small, a sufficient supporting effect of the DLC film can be already achieved with a film thickness of 0.5 μm, while the supporting effect is no longer possible with a support layer of 0.3 μm. Not enough. However, a film thickness of at least 1 μm to about 3 μm is usually recommended. Larger film thicknesses, for example 6 μm, can be advantageous, especially by use where high pressures per unit area are generated.

  In addition, a metal intermediate layer with or without a gradual transition may be applied between the support layer and the anti-friction layer, or directly, for example, the carbon content increasing towards the anti-friction layer. A transition layer in the form of a graded layer may be applied.

  The DLC antifriction layer itself is therefore advantageously implemented as follows: a metal intermediate comprising at least one metal Me from the IV, V, VI subgroup elements, Al or Si in the direct support layer Deposit the layer. It is preferred to use an intermediate layer from the element Cr or Ti which has been found to be particularly suitable for this purpose. However, nitride, carbide, boride or oxide intermediate layers or intermediate layers in which a mixture of one or more metals and one or more of the above non-metals is used are also possible. May be applied even on a metal matrix with or without a gradual transition. If the carbon-friction layer is applied directly to the adhesive layer, this intermediate layer can be omitted if the adhesive layer itself is made of a metal or a compound suitable as an adhesive layer.

  In this, or alternatively directly, without an intermediate layer, preferably the transition layer is in particular a graded layer, in the course of this layer the metal content decreases perpendicularly to the workpiece surface and the C content increases. It continues in the form of The increase in carbon can then be effected in some cases by increasing various carbide phases, by increasing free carbon, or by mixing this type of phase with the metal phase of the intermediate layer. The thickness of the graded layer can then be adjusted by adjustment of the appropriate course ramp, as is known to those skilled in the art. The increase of the C content or the decrease of the metal phase can be performed continuously or stepwise, and the alignment of the metal monolayer and the C-rich monolayer in at least a part of the graded layer is due to the further collapse of the film tension. May be provided. In that case, for example, starting from a MeC film applied, for example, by sputtering, the free carbon content can be increased continuously or stepwise by the addition of a carbon-containing reaction gas. In that case, for example, for films on tungsten carbide bases, a ratio of about 50: 1 to about 2: 1 of carbon bonded as carbide to free carbon has been found to be advantageous. Similar relationships could be confirmed for films on chromium carbide, tantalum carbide or molybdenum carbide bases.

  Due to the formation of the graded layer, the material properties of the supporting and DLC films (eg elastic modulus, structure, etc.) are adapted to each other almost continuously and thereby to the normally occurring metal or Si / DLC film interface. Counteracts the risk of crack formation along.

  Termination of the DLC anti-friction layer can be accomplished by switching off the sputtering and / or bias supply when a defined flow rate of the carbon-containing process gas is achieved or when a certain pressure is achieved. Another method is to keep the coating parameters constant during the last process step in order to keep the properties of the outer functional layer constant throughout the desired minimum film thickness.

  In that case, the hardness of the entire carbon layer is adjusted to a value greater than 0.8 GPa, in particular 10 GPa or more. In this case, even when the film thickness is> 1 μm, particularly> 2 μm, on the steel specimen having a hardness of about 60 HRC. VDI 3824, the same or better than HF3 with sheet 4, but especially the same adhesion strength with HF1. By measuring the contact resistance of the DLC film according to the present invention, a value between δ = 0.1 mΩ and δ = 90 mΩ is obtained, and in this case, in particular, the value is adjusted to a value of 0.5 mΩ to 10 mΩ. This is because a δ value of less than 5 mΩ can only be achieved by adding a large amount of noble metal, which significantly increases the manufacturing cost, and on the other hand, for several uses a contact resistance of more than 10 mΩ is already present. Because it is too big.

At the same time, the carbon layer has a low coefficient of friction typical of Me-carbon, in particular film roughness R _a = 0.01 to 0.04; R _z DIN <0.8, in particular pin-on It is characterized by μ ≦ 0.2 in the disk test.

  The growth rate is about 1 to 3 μm / h and depends on the load and support in addition to the process parameters. In this case in particular, it has an influence on whether the member to be coated is fixed in one, two or three turns to the magnet holder or whether it is clamped or inserted. The overall mass of the holder and the plasma transmission rate are also important, so higher growth rates and overall with a lightweight holder, for example by using, for example, a spoke disc instead of a solid disc A better film quality is achieved. The membrane tension can be 0.8 GPa and is therefore within the normal range of hard DLC membranes. Furthermore, such membranes have a slightly lower hardness (9-15 GPa) and a significantly lower coefficient of friction, and the insertion force generated by this coefficient of friction is reduced.

  Furthermore, these properties can be obtained with small amounts of the elements Ag, Au, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Os, Rh, Ru, W and / or alloys thereof, such as Co sputtering, vapor deposition, target materials. Alternatively, it can be improved by addition, by alloying to the like, and / or stabilized against corrosion / oxidation. If a particularly good conductivity is to be achieved, a residual metal content of at least 30 to a maximum of 60%, in particular 40-50%, can be advantageously defined in the final layer set.

  Because of the excellent mechanical properties of such metal-containing DLC films, these metal-containing DLC films are also advantageously used when the bearing function of the coated conductive material is additionally desired. be able to. For example, such a conductive material used for transmitting electrical signals at the same time can be advantageously used for bearings.

EXAMPLES Next, the present invention will be described in various ways. All Me-DLC membranes or support layers are modified on a copper material at a temperature below 250 ° C., for example in DE 10018143 in FIG. 1 and the description [0076] to [0085] belonging thereto It was deposited on a Balzers BAI 830 C production device. Furthermore, all the coatings were subjected to pretreatments, for example known from Method Example 1 of the above specification, with heating and etching using low voltage. Correspondingly indicated parts of the above published specification are declared to be incorporated components of the present application.

Comparative Example 1
Here, the final, ie metal-containing DLC antifriction layer in the outer layer area, was applied on CuSn8 bronze with a chromium adhesion layer but without an additional support layer. After the above pretreatment, an additional chromium adhesion layer was applied in the same manner as in Method Example 1 of DE 10018143.

  Subsequently, as the Cr target was activated, six WC targets were activated with a power of 1 kW each, and both target types were left running simultaneously for 2 minutes. At that time, the power of the WC target is increased from 1 kW to 3.5 kW in 2 minutes at the same Ar flow rate. At the same time, the negative substrate voltage on these members is increased to 300 V in a ramp shape in 2 minutes from the voltage 0 V applied to the end of the Cr adhesive layer. This 300V is achieved when the WC target is operated at maximum power. Subsequently, the Cr target is switched off. The WC target is left running at a constant Ar flow rate and power 3.5 kW for 6 minutes, then the acetylene gas flow rate is increased to 200 sccm over 11 minutes and maintained constant for 60 minutes with the parameters listed in Table 1. Subsequently, the coating process is terminated.

Example 2
The difference from Example 1 is that the acetylene gas flow rate is only increased to 80 sccm in 5 minutes in the last process step and maintained in that amount for 60 minutes.

Example 3
The difference from Example 1 is that the acetylene gas flow rate is increased to 30 sccm in 2 minutes and maintained in that amount for 60 minutes in the last process step.

Comparative Example 4
The difference from Example 1 is that no acetylene gas is added and the WC target is operated at a constant Ar flow rate for 60 minutes after the Cr target is switched off.

Example 5
For Example 5, a CrN support layer was first deposited, followed by applying a Me-DLC conductive layer on the support layer as in Example 3. The CrN support layer was deposited according to the parameters described in Table 5), in which a low-voltage arc discharge was additionally ignited on the central axis between the hot cathode and the auxiliary anode in order to increase the plasma density.

Example 6
For Example 6, a chromium adhesion layer was first applied as in Example 1. The subsequent functional layer containing WC was doped with Ag.

  In addition, when the Cr target is activated, the four WC targets are activated with 1 kW of power each, and both target types are left running simultaneously for 2 minutes, with the WC target power remaining the same as Ar Increase the flow rate from 1 kW to 3.5 kW in 2 minutes. Similarly, two silver targets attached to the coating apparatus are ignited simultaneously with the WC target, and the power is increased from 0 to 1 kW in the same time. At the same time, the negative substrate voltage on these members is increased to 300 V in a ramp shape in 2 minutes from the voltage 0 V applied to the end of the Cr adhesive layer. Subsequently, the Cr target is switched off. The WC- and Ag targets are operated together at a constant Ar flow for 6 minutes, then the acetylene gas flow is increased to 30 sccm in 2 minutes and the parameters according to Table 6 are kept constant for 60 minutes during the last coating phase.

Membrane Evaluation As can be seen from Table 7, the prior art membrane has a relatively high contact resistance, as described in Comparative Examples 1 and 4. As a typical example in this case, Example 1 shows an aC: H: Me- or Me-DLC film having a significant C content toward the surface. Example 4 shows a carbide film with no significant free carbon content.

  The measured values described were determined at 10 s each after 100 g of contact weight (Kontaktgewich) was applied through calculation of the average value at five different measurement points. The tip of the contact weight is made of gold with a diameter of 3 mm. The measurement of each value was confirmed by reference measurement before and after gold.

  The measurement of the friction force of the plug-in connection was carried out on a macro friction test stand (Makloverschleisspruestand) on:

DLC plug Standard plug
(Tinning)
Specimen Geometry Rider-on-flat Rider-on-flatrider diameter 4mm 4mm
Contact surface 0.3 mm ² 0.3 m ²
Test atmosphere Dry Dry frequency 1 cycle at 2.5 s 1 cycle test time at 2.5 s 3000 cycles 25 cycles Normal force 20N 5N
Friction stroke (Reibweg) 3mm 3mm

  The display of the friction force after the defined number of cycles indicates the wear of the sample. The tinned standard plug has a friction force of 1000 mN after 25 cycles. Increasing the number of cycles beyond 30 results in complete destruction. Values for DLC coated plugs are in the third column.

  Surprisingly, this test revealed that films whose free carbon content was in the middle range (Examples 2-3) had significantly lower contact resistance. This low contact resistance remained the same for the application of an additional CrN support layer as described in Example 5. Contact resistance could be further reduced by Ag Co sputtering as described in Example 6.

Claims (20)

  In a conductive material comprising a copper-containing alloy for use as a plug or clamp connection having a cover layer comprising at least an adhesive layer and a carbon-containing antifriction layer deposited on at least a portion of the contact surface, A conductive material, wherein the anti-friction layer has a carbon content of 40 atomic% to 70 atomic%.   The conductive material according to claim 1, wherein the anti-friction layer is a hard film and contains diamond-like carbon.   The antifriction layer additionally comprises at least one element from groups IV, V and VI of the periodic table (ie Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W) or Si. The conductive material according to claim 1, comprising a metal Me.   4. The conductive material according to claim 3, wherein the anti-friction layer comprises a metal carbide film and a metal carbide film attached to the metal carbide film and having a free carbon content increasing toward the surface. .   Conductive metal according to claim 4, characterized in that the metal carbide film is a carbide of elements of groups IV, V and VI of the periodic table, in particular tantalum carbide, molybdenum carbide, chromium carbide or tungsten carbide base. Sex material.   6. Conductivity according to any one of claims 1 to 5, characterized in that a support layer is provided between the adhesive layer and the anti-friction layer or the adhesive layer is implemented as a support layer. material.   The support layer is an element of groups IV, V and VI of the periodic table (ie, Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W) or at least one metal Me from aluminum or Si The conductive material according to claim 6, comprising:   The support layer is additionally or exclusively one or more hard material compounds comprising at least one metal Me and at least one non-metal, wherein the metal is a subgroup of elements IV, V and VI of the periodic table of elements. A group element (ie, Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W), at least one of aluminum or Si and the non-metal is at least one of the elements C, N, B or O 7. Conductive material according to claim 6, characterized in that it contains carbon in particular.   9. Conductive material according to any one of claims 6 to 8, characterized in that a transition layer is applied between the support layer and the antifriction layer.   The transition layer is an element of groups IV, V and VI of the periodic table (ie, Ti, Zr, Hf; V, Nb, Ta; Cr, Mo, W) or at least one metal Me from aluminum or Si The conductive material according to claim 9, comprising:   The conductive material according to claim 9, wherein the transition layer is a graded layer, wherein the C content of the transition layer increases toward the anti-friction layer.   Adhesive layer and / or support layer, but especially at least the anti-friction layer in small amounts of the following elements: Ag, Au, Cu, Fe, Ir, Mo, Ni, Pd, Pt, Os, Rh, Ru, W and / or these The conductive material according to claim 1, comprising at least one of the following alloys.   The conductive material according to any one of claims 6 to 11, wherein the thickness of the support layer is 0.5 to 6 µm, particularly 1 to 3 µm.   The conductive material according to claim 1, wherein the contact resistance is 0.1 to 90 mΩ, particularly 0.5 mΩ to 10 mΩ.   The conductive material according to claim 1, wherein the copper-containing alloy is copper, bronze, brass or western silver.   The conductive material according to claim 1, wherein the copper-containing alloy is pre-coated by plating.   2. The conductive material according to claim 1, wherein the copper-containing alloy is pre-coated by plating with Cr, Ni or CrNi alloy.   Electrical contact piece comprising or consisting of a conductive material according to any one of the preceding claims.   A conductive semi-finished product comprising at least one electrical contact piece according to claim 18.   A conductive strip or profile comprising at least one electrical contact piece according to claim 19.